This invention relates broadly to the field of a safety valve method and apparatus and particularly to a ball-type subsurface safety valve for wells.
In my U.S. Pat. No. 3,901,321 there is an extensive consideration of the problems to be solved and the state of the prior art with respect to subsurface safety valves and in particular ball-type subsurface safety valves and reference is hereby made to that patent for incorporation herein for all purpose and in particular for the prior art and the consideration of the prior art set forth therein. From this prior art consideration two primary operating problems effecting reliability of subsurface safety valves primarily emerge--the inherent mechanical or frictional resistance to operating movement and differential well pressure loading of the closure element during opening. The valve disclosed therein overcomes these problems by spacing both seats from the ball for equalizing the differential well pressure across the ball prior to opening the ball by moving the ball longitudinally downward with a pair of support pins concentrically engaging the ball on opposite sides thereof. The disclosed valve was of complex construction in that it employed upper and lower operator members, each of which was spring biased and fluid pressure responsive. Prior to and since the filing of my application on Dec. 26, 1973 maturing into U.S. Pat. No. 3,901,321, a number of additional patents have issued furthering the present state of the art with respect to the present invention and which should be considered.
U.S. Pat. No. 3,771,603 to Crowe discloses the use of rotational movement limiting stops formed between the ball cage and the ball closure element. The eccentric pins engaging the ball for effecting rotation are fixed in the ball and the ball element is moved longitudinally relative to the pivot pins for effecting rotational movement by upper and lower sleeves sealingly engaging the ball for reciprocating the ball in opposite directions to effect the desired operation. Well fluid pressure equalization about the ball element is achieved prior to effecting operning rotation by a lost motion arrangement with the operator sleeve to minimize differential well pressure loading in a manner similar to that disclosed in my U.S. Pat. No. 3,7662,471. As the primary closing spring is located to urge on the lower operator sleeve and the fluid pressure responsive surfaces for effecting opening is located on the upper operator sleeve, the "gross force" required for overcoming the urging of the closing spring and rotating the ball must be transmitted through the sealing engagement with the ball. As the frictional force opposing rotation is a function of the magnitude of the force between the operator seats and the ball the transmitting of the "gross force" through the ball inherently increases the frictional resistance to rotation. U.S. Pat. No. 3,796,257 to Hudson operates in a similar manner. U.S. Pat. No. 3,827,494 to Crowe and entitled "Anti-Friction Ball Valve Operating Means" discloses an arrangement for effecting support of the ball during rotation similar to that disclosed in my copending application Ser. No. 212,260, filed Dec. 27, 1971. A resilient secondary upper seat is disclosed in this Crowe patent as being disposed outwardly and adjacent the upper operator sleeve (such as disclosed in U.S. Pat. No. Re. 28,131 of U.S. Pat. No. 3,741,249) with the upper operator sleeve engaging the ball for longitudinally moving the ball downwardly relative to the fixed eccentric pins to effect rotation of the ball to the open position. The spring biased lower operating sleeve sealingly engages the ball element and carries movably mounted thereon and in concentric outwardly relationship a sleeve having a pair of upwardly projecting support fingers that concentrically engage the ball on opposite sides thereof for carrying part of the "gross force" to effect operation and thereby partially reducing the rotation resisting frictional forces of the upper and lower operator sleeves acting on the sealing surface of the ball.
In U.S. Pat. No. 3,868,995, also to Crowe, there is disclosed a subsurface safety valve minimizing well pressure loading on the ball by providing a vent valve through the ball element in a manner somewhat similar to that disclosed in my U.S. Pats. Nos. 3,667,557 and 3,763,940. In this Crowe patent, concentric pins mounted on the operator sleeve engage the ball base for moving the ball base longitudinally from the ball cap to expose a vent by-pass in the ball cap for equalizing well fluid pressure across the ball cap. The ball cap is not moved from sealing engagement with the upper operator sleeve during opening rotation although the ball is spaced from the secondary resilient seat prior to rotation. Eccentric pins secured with the housing effect rotation of the ball as the ball moves toward the stationary lower seat when in the open position. The member mounting the concentric pins in engagement with the ball transmits the gross force to the spring independent of the sealing force of the primary operator sleeve which follows the ball downwardly by the force of control fluid pressure. Thus only a "net force" is imparted to the ball for effecting rotation and such net operating force is imparted to the ball through pins engaging the ball on opposide sides thereof.
Taylor U.S. Pat. No. 3,826,462 primarily emphasizes the disclosed large diameter ball feature in a wireline retrievable valve and which is also disclosed in my earlier filed U.S. Pat. Nos. 3,762,471 and 3,870,102. In the Taylor disclosure, the concentric fingers engaging the ball move longitudinally, but do not effect longitudinal movement of the ball as they serve only as a movement guide. The eccentric pins engaging the ball are fixed with the cage and there is no spacing from the upper and lower seats which are used for effecting the longitudinal movement of the ball resulting in the desired rotational move. The closing spring is also located below the ball element and therefore the gross force is transmitted through the ball for effecting operation.
U.S. Pat. No. 3,847,218 to Boyadjieff et al. discloses a rotatable ball valve in which the ball is rotated closed when in the lower position and is therefore reversed from the usual operation where the ball is rotated open when in the lower position. In this patent the ball element is pulled longitudinally upwardly by a cage member having concentric pins engaging the ball with the eccentric pins fixed with the housing for rotating the longitudinally moving ball. The disclosed ball element engages a stationary resilient sealing seat when in the lower position and moves away from the resilient seat when being pulled upwardly to the open position. From the disclosure it is not clear whether there is spacing prior to rotation as in U.S. Pat. No. Re. 28,131 or if the ball merely rotates off the seat as in Barrington U.S. Pat. No. 3,347,318.
U.S. Pat. No. 3,398,762 discloses a ball-type subsurface safety valve in which the ball is rotated about a pair of longitudinal axis in moving to and from the open and closed positions to minimize frictional resistance to the rotation. There is no disclosure of spacing the ball from the seats to minimize frictional resistance to rotation.
Radig U.S. Pat. No. 3,667,505, like Bostock U.S. Pat. No. 3,894,715, discloses a ball-type safety valve in which a longitudinal reciprocating operator member is connected with the ball element for effecting rotation of the ball element. The ball element is restricted against longitudinal movement with the operator by constant engagement with upper and lower annular seats that provide frictional resistance to rotation by the ball element even though only a net force is transmitted to the ball element.